If you have successfully entered three stocks, and you have trouble with the forth one we should first take a look at your entries, and if necessary, clear the transaction and start over.
The three boxes we should first look at are:
If these three boxes are entered correctly that is a good start. Be aware that if you have an entry in box 1g - Wash sale, you will not get credit for a loss on that stock.
Now check and see if anything else has been entered. Many times there is not.
If all seems in order I suggest we clear this transaction and re-enter it.
If you have to delete an individual entry from your return you can go back to the input screen. On the right hand side there is a trash can. Select the trash can and confirm you want to delete that form.